#define _CRT_SECURE_NO_WARNINGS 1

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* _buildTree(vector<int>& preorder, vector<int>& inorder, int& prei, int inbegin, int inend)
    {
        if (inbegin >= inend)
            return nullptr;

        TreeNode* root = new TreeNode(preorder[prei]);
        int i;
        for (i = inbegin; i < inend; i++)
        {
            if (preorder[prei] == inorder[i])
                break;
        }
        prei++;

        root->left = _buildTree(preorder, inorder, prei, inbegin, i);
        root->right = _buildTree(preorder, inorder, prei, i + 1, inend);

        return root;
    }
    TreeNode* buildTree(vector<int>& preorder, vector<int>& inorder) {
        int prei = 0;
        return _buildTree(preorder, inorder, prei, 0, inorder.size());
    }
};